In recent years, electronic apparatuses such as an image pickup apparatus, that each photograph a subject such as a person to generate an image (image data) and record the generated image (image data) as an image content (image file) have prevailed, the image pickup apparatus being exemplified by a digital still camera. As an image pickup device used in such electronic apparatuses, a CCD (Charge Coupled Sensor) sensor, a CMOS (Complementary Metal Oxide Semiconductor) sensor, and the like are widely used.
There is a dynamic range as one of performance axes of image sensors. The dynamic range is a width of brightness of incident light that can be converted into an effective image signal. The larger the dynamic range, the higher the performance is since dark light to bright light can be converted into image signals.
For example, Patent Document 1 proposes a system called SVE (Spatially Varying Exposure) for enlarging a dynamic range of an image sensor.
Pixels of normal image sensors include a photodiode (PD) that converts incident light into charges by a photoelectric conversion. Since an accumulable charge amount of the pixels is determined, a charge overflow occurs with respect to incident light that is too strong, and signals cannot be taken out no more. Further, due to noises generated in pixels and a circuit for reading, generated charges are buried in the noises so that signals cannot be taken out with respect to incident light that is too weak.
In this regard, the SVE system is a system in which pixels having different sensitivities are arranged in a predetermined arrangement pattern so that signals can be acquired from pixels having a high sensitivity in a dark part of a scene and pixels having a low sensitivity in a bright part of the scene. As a method of changing the sensitivity for each pixel, there is a method that uses an electronic shutter control mechanism of an image sensor in addition to a method of changing a pixel aperture ratio and a method that uses on-chip filters having different optical transmittances. Patent Document 1 proposes a method that uses an electronic shutter control mechanism in a CCD image sensor.
Patent Document 2 proposes an image sensor in which 4 types of pixels including pixels having a spectral sensitivity for acquiring luminance signals and pixels having 3 types of spectral sensitivities for acquiring color signals are arranged. As an example of such a color arrangement, Patent Document 2 discloses an arrangement in which pixels for acquiring luminance signals are arranged in a checkerboard arrangement and pixels having R, G, and B spectral sensitivities for acquiring color signals are arranged at remaining positions in the checkerboard arrangement.
Patent Document 3 discloses an example of an exposure pattern in a case where an image is taken using the SVE system in the pixel arrangement disclosed in Patent Document 2.
Patent Document 1: Japanese Patent Application Laid-open No. 2007-135200
Patent Document 2: Japanese Patent Application Laid-open No. 2007-243334
Patent Document 3: Japanese Patent Application Laid-open No. 2012-257193